Add file path component to pipeline policy

What does this MR do and why?

Add file path component to pipeline policy

• add file path component
• add override selector for pipeline policy
• conditionally show other message

What does this MR not do and why?

• does not hook up any real functionality yet. Saving all that complicated logic for a future MR

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Scenario	ff on	ff off
Scan Execution Policy
Pipeline Execution Policy		N/A

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Upload a GitLab Ultimate license
2. Enable feature flag

echo "Feature.enable(:pipeline_execution_policy_type)" | rails c

3. Navigate to http://gdk.test:3443/gitlab-org/gitlab-test/-/security/policies/new?type=pipeline_execution_policy
4. Verify the action content (doesn't do anything yet)
5. Navigate to http://gdk.test:3443/gitlab-org/gitlab-test/-/security/policies/new?type=scan_execution_policy
6. Add a new action
7. Verify the user cannot add a file path action
8. Disable the feature flag

echo "Feature.disable(:pipeline_execution_policy_type)" | rails c

9. Verify the user can add a file path action

Related to #454284